Welcome to the board! There are several sellers listed in the marketplace that may be able to help.
I have been able to repair the broken plastic ring with Devcon plastic weld and a hose clamp. If all else fails, I think the MGB unit fits, but the stalks are shorter.
Good luck,
Kurt

And make sure you get the stalks for a LHD car, I forgot to specify that when buying from Moss Europe and got switchgear for an RHD MGB. Works just fine, but looks a bit odd since all the symbols and lettering is upside down...

If you go for the MGB unit, remember that the connector pinout is different. Easy to fix, just has to be done.